Exogenous auxin alleviates cadmium toxicity in Arabidopsis thaliana by stimulating synthesis of hemicellulose 1 and increasing the cadmium fixation capacity of root cell walls
2013
Zhu, Xiao Fang | Wang, Zhi Wei | Dong, Fang | Lei, Gui Jie | Shi, Yuan Zhi | Li, Gui Xin | Zheng, Shao Jian
Auxin is involved in not only plant physiological and developmental processes but also plant responses to abiotic stresses. In this study, cadmium (Cd2+) stress decreased the endogenous auxin level, whereas exogenous auxin (α-naphthaleneacetic acid, NAA, a permeable auxin analog) reduced shoot Cd2+ concentration and rescued Cd2+-induced chlorosis in Arabidopsis thaliana. Under Cd2+ stress conditions, NAA increased Cd2+ retention in the roots and most Cd2+ in the roots was fixed in hemicellulose 1 of the cell wall. NAA treatment did not affect pectin content and its binding capacity for Cd2+, whereas it significantly increased the content of hemicellulose 1 and the amount of Cd2+ retained in it. There were highly significant correlations between Cd2+ concentrations in the root, cell wall and hemicellulose 1 when the plants were subjected to Cd2+ or NAA+Cd2+ treatment for 1 to 7d, suggesting that the increase in hemicellulose 1 contributes greatly to the fixation of Cd2+ in the cell wall. Taken together, these results demonstrate that auxin-induced alleviation of Cd2+ toxicity in Arabidopsis is mediated through increasing hemicellulose 1 content and Cd2+ fixation in the root, thus reducing the translocation of Cd2+ from roots to shoots.
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